1. Field of the Invention
The present invention relates to an ink composition for an etching resist, a method of forming an etching resist pattern using the same, and a method of forming a microchannel using the ink composition.
2. Description of the Related Art
An etching resist, which is an etching-resist thin film used to form a pattern by etching, is mainly used in manufacturing processes for semiconductor circuits and printed circuit boards. In such manufacturing processes, a photoresist that is photo reactive is typically used as the etching resist. A process for forming an etching resist pattern using the photoresist will now be described. First, a liquid photoresist is coated on a surface in which a pattern is to be formed by spin coating or similar methods to form a film. Alternatively, a dry photoresist film can be disposed on the surface by attaching or using a similar method. Then, ultraviolet rays, an electron beam or the like is selectively radiated onto a portion of the photoresist film where a pattern is to be formed or where the pattern is not to be formed using a photo-mask with the pattern. As a result, a chemical reaction occurs only in the irradiated portion. Subsequently, only a portion of the photoresist that covers the surface to be etched is removed through a developing process to form a pattern. Then, the portion of the surface that is not covered by the photoresist is selectively etched through the etching process. Finally, the photoresist material that covers a non-etched region is removed by stripping.
Although the method of forming an etching resist pattern using a photoresist is useful for forming a micro pattern, the photoresist is formed on the entire surface of a substrate even though this is unnecessary to prevent etching. In addition, all photoresist methods require an exposure process, in which an expensive exposure apparatus is used, and a photomask with a pre-designed pattern. The designing and manufacturing of the photomask requires a great amount of time.
Meanwhile, when a pattern has a large size and does not require high precision, an etching resist pattern can be formed on the surface of a substrate to be etched through an open portion of a mask having a desired pattern; the pattern can be directly drawn on the surface of a material to be etched using an etching mask material; the etching resist material can be coated on the entire surface of the substrate and then only an etching resist material covering a portion where a pattern is to be formed can be scratched to be removed; or the etching resist pattern can be formed by stamping, printing, or the like. However, these processes are expensive and require a long time because they must be performed manually. In some cases, stamps and printed board that are patterned in advance are required.
In order to overcome these problems, an etching resist material can be formed in a pattern on a substrate to be etched using an inkjet technique which is disclosed in Japanese Patent Publication Nos. sho 56-66089, sho 62-181490, and hei 9-8436 and International Patent GB9912437 (WO 01/11426). In these patents, the etching resist material is sprayed using an inkjet nozzle and then an etching process is performed to form a desired pattern. That is, according to this method, after a pattern is designed using a computer, an etching resist can be formed in a pattern directly on a substrate using an inkjet printer. As a result, the processing time and costs can be decreased.
In general, an ink composition for an etching resist used in the inkjet technique is formed by dispersing or dissolving a polymer additive, a pigment, or the like in an organic solvent. The polymer additive is typically an acryl resin, a nobolak resin, or the like, which easily dissolves or disperses in the organic solvent and has excellent etching resistance.
However, the organic solvent that is used in the ink composition pollutes the environment, and is not suitable for forming a micro pattern due to its small contact angle with respect to a substrate. These problems can be overcome by replacing the organic solvent with water or with water and an aqueous solvent. In this case, a polymer additive that easily dissolves or disperses in water and the aqueous solvent is used instead of the polymer additive described above.
Meanwhile, the ink composition for an etching resist must be highly adhesive to a metal substrate, and have high resistance against an etching solution containing water, hydrochloric acid, and iron chloride used in a subsequent etching process.
The ink composition for an etching resist that is used in Patent GB9912437 (WO 01/11426) is cured using ultraviolet rays or an electron beam. In this patent, the ink composition is not described in detail, but in general, a photo-curable ink is necessarily accompanied by a relatively expensive photo initiator. In addition, when the electron beam is used, an electron beam apparatus must be used in a vacuum. Accordingly, an ink composition that can form a hard thin layer by drying or thermal curing instead of using ultraviolet rays or an electron beam is preferable.